Conventional piezoresponse signal readout techniques, such as piezoresponse force microscopy (PFM) rely on the detection of bit signals from a ferroelectric memory medium by virtue of a cantilever probe tip sensor's mechanical motion on the surface of the medium. Such probe storage devices typically use two parallel plates. A first plate includes the cantilevers with contact probe tips extending therefrom for use as read-write heads and a second, complementary plate includes memory media for storing data. The plates can be moved relative to one another in an X-Y plane while controlling the Z-spacing between the plates. Motion of the plates relative to one another allows scanning of the memory media by the contact probe tip and data transfer between the two.
Disadvantageously, PFM relies on complex laser and optical setup for alignment and detection of the cantilever probe tip deflection, which deflection is typically less than about 1 nm. In PFM, the laser beam is focused onto the cantilever probe tip by using the optical setup. The reflected laser beam from the cantilever probe tip is then aligned to a center of a photodiode detector. In PFM, an AC voltage is applied between the cantilever probe tip and the ferroelectric sample. The AC voltage results in an expansion and contraction of the ferroelectric at the same frequency as a frequency of the AC voltage. Consequently, the cantilever probe tip deflects in unison with the expansion and contraction of the ferroelectric sample, in this way causing the reflected laser beam to oscillate about the center of the photodiode detector. The changing position of the reflected laser beam relative to the center of the photodiode detector in turn generates current which PFM uses to calculate the cantilever tip deflection.
Alternatively, a conventional scanning nonlinear dielectric microscopy (SNDM) technique may be used to read bits. SNDM, however, disadvantageously requires complicated resonance circuitry operating at the GHz range to detect atto-farad ranges in capacitance. SNDM aims to detect changes in capacitance as the tip goes from an UP domain to a DOWN domain. However, this change in capacitance has proven to be extremely difficult to detect, requiring complicated circuitry operating at high frequencies. SNDM further requires that the tip be made coaxial in order to provide a constant impedance environment for the system, in this way adding to the complexity of the same.
The prior art fails to provide an arrangement and method that avoid the need for complex optical setups and/or for complex resonance circuitry operating in the GHz range as noted above.
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